DEBT OBLIGATIONS - Schedule of Debt Obligations (Details) - USD ($)	9 Months Ended
	Sep. 30, 2023	Dec. 31, 2022
Debt Instrument [Line Items]
Outstanding Face Amount	$ 23,677,829,000
Carrying Value	$ 23,570,235,000	$ 21,356,679,000
Weighted Average Funding Cost	6.40%
Weighted Average Life (Years)	1 year
MSR purchase price holdback	$ 215,276,000	87,700,000
US Treasury Bill Securities
Debt Instrument [Line Items]
Repurchase agreements	974,000,000
Secured Financing Agreements
Debt Instrument [Line Items]
Outstanding Face Amount	13,605,832,000
Carrying Value	$ 13,605,380,000	11,257,736,000
Weighted Average Funding Cost	6.00%
Weighted Average Life (Years)	3 months 18 days
MSR purchase price holdback	$ 199,500,000
Secured Notes and Bonds Payable
Debt Instrument [Line Items]
Outstanding Face Amount	10,071,997,000
Carrying Value	$ 9,964,855,000	10,098,943,000
Weighted Average Funding Cost	6.80%
Weighted Average Life (Years)	1 year 10 months 24 days
Warehouse Credit Facilities-Residential Mortgage Loans | Warehouse Credit Facilities
Debt Instrument [Line Items]
Outstanding Face Amount	$ 2,155,544,000
Carrying Value	$ 2,155,092,000	2,601,327,000
Weighted Average Funding Cost	7.30%
Weighted Average Life (Years)	8 months 12 days
Repurchase agreements	$ 244,300,000
Interest rate	5.10%
Warehouse Credit Facilities-Residential Mortgage Loans | Warehouse Credit Facilities | Collateral
Debt Instrument [Line Items]
Weighted Average Life (Years)	17 years 9 months 18 days
Outstanding Face of Collateral	$ 2,565,299,000
Amortized Cost Basis of Collateral	2,586,513,000
Carrying Value of Collateral	2,482,541,000
Warehouse Credit Facilities - Mortgage Loans Receivable | Warehouse Credit Facilities
Debt Instrument [Line Items]
Outstanding Face Amount	1,212,156,000
Carrying Value	$ 1,212,156,000	1,220,662,000
Weighted Average Funding Cost	8.20%
Weighted Average Life (Years)	3 months 18 days
Warehouse Credit Facilities - Mortgage Loans Receivable | Warehouse Credit Facilities | Collateral
Debt Instrument [Line Items]
Weighted Average Life (Years)	1 year 1 month 6 days
Outstanding Face of Collateral	$ 1,473,515,000
Amortized Cost Basis of Collateral	1,471,904,000
Carrying Value of Collateral	1,471,904,000
Agency RMBS or U.S Treasury Bills | Secured Financing Agreements
Debt Instrument [Line Items]
Outstanding Face Amount	9,653,355,000
Carrying Value	$ 9,653,355,000	6,821,788,000
Weighted Average Funding Cost	5.40%
Weighted Average Life (Years)	2 months 12 days
Agency RMBS or U.S Treasury Bills | Secured Financing Agreements | Collateral
Debt Instrument [Line Items]
Weighted Average Life (Years)	8 years 1 month 6 days
Outstanding Face of Collateral	$ 9,731,596,000
Amortized Cost Basis of Collateral	9,546,319,000
Carrying Value of Collateral	9,870,841,000
Non-Agency RMBS | Secured Financing Agreements
Debt Instrument [Line Items]
Outstanding Face Amount	574,346,000
Carrying Value	$ 574,346,000	609,282,000
Weighted Average Funding Cost	7.30%
Weighted Average Life (Years)	9 months 18 days
Non-Agency RMBS | Secured Financing Agreements | Collateral
Debt Instrument [Line Items]
Weighted Average Life (Years)	6 years 2 months 12 days
Outstanding Face of Collateral	$ 13,600,138,000
Amortized Cost Basis of Collateral	882,800,000
Carrying Value of Collateral	880,999,000
SFR properties
Debt Instrument [Line Items]
Carrying Value	797,027,000	822,372,000
SFR properties | Secured Financing Agreements
Debt Instrument [Line Items]
Outstanding Face Amount	10,431,000
Carrying Value	$ 10,431,000	4,677,000
Weighted Average Funding Cost	7.80%
Weighted Average Life (Years)	1 year 2 months 12 days
SFR properties | Secured Financing Agreements | Collateral
Debt Instrument [Line Items]
Amortized Cost Basis of Collateral	$ 32,899,000
Carrying Value of Collateral	32,899,000
SFR properties | Secured Notes and Bonds Payable
Debt Instrument [Line Items]
Outstanding Face Amount	833,387,000
Carrying Value	$ 786,596,000	817,695,000
Weighted Average Funding Cost	4.10%
Weighted Average Life (Years)	3 years 7 months 6 days
SFR properties | Secured Notes and Bonds Payable | Minimum
Debt Instrument [Line Items]
Interest rate	3.50%
SFR properties | Secured Notes and Bonds Payable | Maximum
Debt Instrument [Line Items]
Interest rate	7.10%
SFR properties | Secured Notes and Bonds Payable | Collateral
Debt Instrument [Line Items]
Amortized Cost Basis of Collateral	$ 956,118,000
Carrying Value of Collateral	956,118,000
Excess MSRs
Debt Instrument [Line Items]
Carrying Value	193,432,000	227,596,000
Excess MSRs | Secured Notes and Bonds Payable
Debt Instrument [Line Items]
Outstanding Face Amount	193,432,000
Carrying Value	$ 193,432,000	227,596,000
Weighted Average Funding Cost	8.80%
Weighted Average Life (Years)	1 year 10 months 24 days
Excess MSRs | Secured Notes and Bonds Payable | Collateral
Debt Instrument [Line Items]
Weighted Average Life (Years)	6 years 3 months 18 days
Outstanding Face of Collateral	$ 61,988,328,000
Amortized Cost Basis of Collateral	239,154,000
Carrying Value of Collateral	278,059,000
MSRs | Secured Notes and Bonds Payable
Debt Instrument [Line Items]
Outstanding Face Amount	4,200,200,000
Carrying Value	$ 4,191,504,000	4,791,543,000
Weighted Average Funding Cost	6.90%
Weighted Average Life (Years)	1 year 8 months 12 days
MSRs | Secured Notes and Bonds Payable | Collateral
Debt Instrument [Line Items]
Weighted Average Life (Years)	7 years 10 months 24 days
Outstanding Face of Collateral	$ 523,532,413,000
Amortized Cost Basis of Collateral	6,317,954,000
Carrying Value of Collateral	8,616,793,000
Servicer Advance Investments | Secured Notes and Bonds Payable
Debt Instrument [Line Items]
Outstanding Face Amount	275,952,000
Carrying Value	$ 275,142,000	318,445,000
Weighted Average Funding Cost	7.50%
Weighted Average Life (Years)	4 months 24 days
Servicer Advance Investments | Secured Notes and Bonds Payable | Collateral
Debt Instrument [Line Items]
Weighted Average Life (Years)	8 years 7 months 6 days
Outstanding Face of Collateral	$ 314,165,000
Amortized Cost Basis of Collateral	361,325,000
Carrying Value of Collateral	$ 387,669,000
Servicer Advances | Secured Notes and Bonds Payable | Secured Overnight Financing Rate | Minimum
Debt Instrument [Line Items]
Variable interest rate spread	1.50%
Servicer Advances | Secured Notes and Bonds Payable | Secured Overnight Financing Rate | Maximum
Debt Instrument [Line Items]
Variable interest rate spread	3.70%
Servicer Advances | Secured Notes and Bonds Payable
Debt Instrument [Line Items]
Outstanding Face Amount	$ 2,091,447,000
Carrying Value	$ 2,091,185,000	2,361,259,000
Weighted Average Funding Cost	7.60%
Weighted Average Life (Years)	6 months
Servicer Advances | Secured Notes and Bonds Payable | Collateral
Debt Instrument [Line Items]
Weighted Average Life (Years)	8 months 12 days
Outstanding Face of Collateral	$ 2,555,898,000
Amortized Cost Basis of Collateral	2,434,266,000
Carrying Value of Collateral	2,434,266,000
Residential Mortgage Loans | Secured Notes and Bonds Payable
Debt Instrument [Line Items]
Outstanding Face Amount	650,000,000
Carrying Value	$ 650,000,000	769,988,000
Weighted Average Funding Cost	6.50%
Weighted Average Life (Years)	7 months 6 days
Residential Mortgage Loans | Secured Notes and Bonds Payable | Collateral
Debt Instrument [Line Items]
Weighted Average Life (Years)	29 years 2 months 12 days
Outstanding Face of Collateral	$ 654,975,000
Amortized Cost Basis of Collateral	655,576,000
Carrying Value of Collateral	658,402,000
Consumer Loans
Debt Instrument [Line Items]
Carrying Value	1,269,768,000	299,498,000
Consumer Loans | Secured Notes and Bonds Payable
Debt Instrument [Line Items]
Outstanding Face Amount	1,303,517,000
Carrying Value	$ 1,269,768,000	299,498,000
Weighted Average Funding Cost	7.10%
Weighted Average Life (Years)	4 years 6 months
Consumer Loans | Secured Notes and Bonds Payable | Collateral
Debt Instrument [Line Items]
Weighted Average Life (Years)	1 year 8 months 12 days
Outstanding Face of Collateral	$ 1,475,494,000
Amortized Cost Basis of Collateral	1,422,559,000
Carrying Value of Collateral	1,436,080,000
Mortgage Loans Receivable
Debt Instrument [Line Items]
Carrying Value	1,719,384,000	1,733,581,000
Mortgage Loans Receivable | Secured Notes and Bonds Payable
Debt Instrument [Line Items]
Outstanding Face Amount	524,062,000
Carrying Value	$ 507,228,000	$ 512,919,000
Weighted Average Funding Cost	5.70%
Weighted Average Life (Years)	3 years 1 month 6 days
Interest rate	4.70%
Face amount of debt at fixed rate	$ 238,100,000
Mortgage Loans Receivable | Secured Notes and Bonds Payable | Collateral
Debt Instrument [Line Items]
Weighted Average Life (Years)	7 months 6 days
Outstanding Face of Collateral	$ 567,432,000
Amortized Cost Basis of Collateral	567,432,000
Carrying Value of Collateral	567,432,000
3.7% Secured Corporate Note | Secured Notes and Bonds Payable
Debt Instrument [Line Items]
Outstanding Face Amount	$ 193,400,000
Interest rate	3.40%
2.5% To 3.5% Agency MSR Secured Note And Bond Payable | Secured Notes and Bonds Payable
Debt Instrument [Line Items]
Outstanding Face Amount	$ 2,700,000,000
2.5% To 3.5% Agency MSR Secured Note And Bond Payable | Secured Notes and Bonds Payable | Secured Overnight Financing Rate | Minimum
Debt Instrument [Line Items]
Variable interest rate spread	2.50%
2.5% To 3.5% Agency MSR Secured Note And Bond Payable | Secured Notes and Bonds Payable | Secured Overnight Financing Rate | Maximum
Debt Instrument [Line Items]
Variable interest rate spread	3.70%
3.0% To 5.4% Public Notes | Secured Notes and Bonds Payable
Debt Instrument [Line Items]
Outstanding Face Amount	$ 1,500,000,000
3.0% To 5.4% Public Notes | Secured Notes and Bonds Payable | Minimum
Debt Instrument [Line Items]
Interest rate	3.00%
3.0% To 5.4% Public Notes | Secured Notes and Bonds Payable | Maximum
Debt Instrument [Line Items]
Interest rate	5.40%
Revolving Warehouse Facility Backed Notes | Secured Notes and Bonds Payable | London Interbank Offered Rate
Debt Instrument [Line Items]
Variable interest rate spread	1.20%
Revolving Warehouse Facility Backed Notes | Secured Notes and Bonds Payable
Debt Instrument [Line Items]
Outstanding Face Amount	$ 650,000,000
Consumer Loan, UPB Class A | Secured Notes and Bonds Payable
Debt Instrument [Line Items]
Interest rate	2.00%
Residential mortgage loan UPB and other collateral	$ 220,900,000
Consumer Loan, UPB Class B | Secured Notes and Bonds Payable
Debt Instrument [Line Items]
Interest rate	2.70%
Residential mortgage loan UPB and other collateral	$ 53,000,000
Consumer Loan, Marcus | Secured Notes and Bonds Payable
Debt Instrument [Line Items]
Outstanding Face Amount	$ 1,000,000,000
Consumer Loan, Marcus | Secured Notes and Bonds Payable | Secured Overnight Financing Rate
Debt Instrument [Line Items]
Variable interest rate spread	3.00%